My Advent of Code solutions in Python.
kevinyap.ca/2019/12/going-fast-in-advent-of-code/
advent-of-code
python
Add solution for 2016/13
+47
+46
2016/day13.py
+46
2016/day13.py
···
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import fileinput
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INPUT = int(fileinput.input()[0])
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def is_open(x, y, input=INPUT):
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"""Open space if number of 1 bits is even, else wall."""
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num = (x * x) + (3 * x) + (2 * x * y) + y + (y * y) + input
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return bin(num)[2:].count('1') % 2 == 0
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def pathfind(a, b, c, d, max_steps=None):
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"""
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Returns length of the shortest path from (a, b) to (c, d)
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and the number of visited locations along the way.
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"""
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deltas = [(0, 1), (1, 0), (0, -1), (-1, 0)]
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horizon = [(a, b)]
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seen = set()
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steps = 0
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while horizon:
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new_horizon = []
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for x, y in horizon:
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if x == c and y == d:
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return steps, len(seen)
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seen.add((x, y))
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for dx, dy in deltas:
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nx, ny = x + dx, y + dy
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if is_open(nx, ny) and nx >= 0 and ny >= 0 and (nx, ny) not in seen:
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new_horizon.append((nx, ny))
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if steps == max_steps:
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break
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horizon = new_horizon
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steps += 1
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return steps, len(seen)
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print "Fewest steps to reach 31, 39 from 1, 1:", pathfind(1, 1, 31, 39)[0]
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print "Distinct locations reached in 50 steps:", pathfind(1, 1, -1, -1, max_steps=50)[1]
+1
2016/input13.txt
+1
2016/input13.txt
···
1
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1350